Generating both power and heat

The Vitovalor is a fuel cell heating appliance that uses the principle of cogeneration to generate both power and heat. To do so, the fuel cell requires not only oxygen but also hydrogen, which is obtained from natural gas in an earlier process.

This technology, especially developed for detached and semi-detached houses, runs at a very high overall level of efficiency and is designed for power-optimised operation.

Hydrogen in the Vitovalor.
Vitovalor 300‑P fuel cell heating appliance cross-section

Construction 

The Vitovalor consists of two units: a fuel cell module and a gas condensing module for covering peak loads. The two units can be transported separately, enabling fast installation even in basement rooms where space is tight. The first unit of the Vitovalor, made by Panasonic, houses the reformer, inverter and fuel cell stack (a series of multiple fuel cells). Before the direct current generated by the fuel cell is fed into the household power circuit, the built-in inverter converts it into alternating current. 

The second unit of the Vitovalor serves primarily to provide heat during times of peak demand. That is, when it is very cold outside or when a lot of hot water is required at short notice. It consists of a gas fuel cell appliance, a DHW cylinder, a heat exchanger and a heating water buffer cylinder with integral indirect coil for DHW heating. Other components in the second unit are a weather-compensated control unit, hydraulic components and an electricity meter. Both units are supplied via a common gas line. They also share a common flue system, which makes installation as easy as for a wall mounted gas condensing boiler.

Cold combustion

The generation of heat and power in the Vitovalor fuel cell heating appliance is based on an electrochemical reaction between two elements: oxygen and hydrogen. The type of combustion that takes place in conventional boilers does not occur, which is why the process is also referred to as cold combustion. 

Although a plentiful supply of hydrogen is available in nature, it does not occur in the form required for cold combustion in the Vitovalor. It must therefore be obtained from natural gas in an earlier process. Depending on requirements, Vitovalor can be operated with natural gas H or bio natural gas. The combustion gas supplied flows through a reformer built into the unit, which uses a catalyst to convert it into hydrogen in a two-stage reaction. 

The first stage of the conversion process produces a mixture of hydrogen and carbon monoxide. In the second, downstream gas cleaning process, carbon monoxide is converted to carbon dioxide.

How Vitovalor works
Fuel Cell Diagram

The Vitovalor in a detached house

[1] Fuel cell module
[2] Peak load boiler
[3] Flue gas/ventilation air system
[4] Integral electricity meter
[5] Communication interface
[6] Electricity meter (bidirectional)
[7] Household power circuit
[8] Public grid
[9] Internet
[10] Vitotrol app
[11] Natural gas E
[12] Water

Efficiency 

When electricity is generated, heat is also produced, which in large, conventional power stations is generally lost as unused waste heat. CHP units such as the Vitovalor on the other hand make use of this waste heat for central and DHW heating. They therefore have a very high level of overall efficiency. Furthermore, there are no losses during energy transfer as the energy is used directly on site. Even the conversion from combustion gas to hydrogen is very efficient due to the absence of intermediate thermomechanical steps. 

The constant electrical output of the fuel cell module is 750 W. A large proportion of the power demand can therefore be covered at all times. The Vitovalor works even more efficiently in combination with the Vitocharge power storage system. This can store surplus power for times of peak load which considerably increases independence from electricity suppliers. Alternatively, it is quite straightforward to export the surplus power to the public grid. The integral energy manager is self-learning and therefore optimises the level of on-site consumption.